of North America with those of Europe. 22.: 



ton group, that it takes its greatest development, while in the 

 states of Ohio and Indiana where these shales are wanting, it is 

 found abundantly in the limestones which form the upper part of 

 the cliff limestone. 



Localities. — Lewis' creek, Charlestown Landing (Indiana) ; Ca- 

 capou, near Hancock (Ya.); Gaspe (Canada) ; Schoharie, Mos- 

 cow, (New York.) In Europe as in America, the P. macropthal- 

 mus is rare in the Silurian system, while it is very abundant in 

 the Devonian beds of the Eifel. In Russia it is found only in 

 the Devonian system of the Altai.* 



Cryphams calli teles, Green. 



stellif 



species 



mem, and at all events, it is impossible to leave them in two dis- 

 tinct genera. If we retain the genus Cryphceus, we should place 

 in it that small division of Phacops having long spines on the tail, 



and which comprises only two species, P. arachnoides and P. 

 stellifer. 



and 



Mr. Mai 



shales of Gahard which are its equivalent. The P. arachnoides 



and stellifer are equally peculiar to the Devonian system of the 

 Eifel. 



Bwmastis barriensis, Murch. — Characteristic of the contem- 

 poraneous beds of Niagara and Wenlock. It occurs at Lock port, 

 (New York,) and Springfield, (Ohio,) in the magnesian lime- 

 stone where it is associated with the P 'entamerus oblon \gu$ \ In the 

 Metalliferous region of Illinois and Wisconsin, it is found in gen- 

 eral also at the base of the upper stage of the Silurian system ; 

 Nevertheless we saw at Galena a specimen in the blue limestone, 

 *Uh species of the lower Silurian stage. 



Horn 



Wenlock 



spec 



and Rochester. It is necessary to unite with this species the 

 " atlas, gigantcus, and hermlaneus of M. de Castelnau. 



C'heiruriis insiguis, Beyr. — This species of which we have 

 fhe head well characterized, has been discovered by Mr. Troost 

 »* Perry county, (Tennessee,) and by us in the siliceous lime- 

 stones of Chicago, (Illinois.) In these two points it belongs to 

 { he upper Silurian sti ' * " * " " '"" 



* [We are not prepared to agree with M. de Verneuil in writing ill these as a sin- 

 g's species. The European species presents difference* of character winch sepa- 

 r *t« it from all the American forms, and that from the Delthyris shaly limestom 

 °« New York, and that from the Schoharie grit are totally distinct species, while 

 that m the Hamilton group is unlike either of them. The one in the Schoharie 

 gnt Us a row of short spines down the back, but usually being preserved as casts, 

 this character is overlooked and the general form relied upon. These differences, 



will be more 



